In the development phase of a product having rotational symmetry, such as a wheel, it is investigated whether there is a registered design similar to the design of the product. However, there is a concern that it will take a lot of time to investigate a huge number of registered designs including foreign registered designs. Therefore, an apparatus which can accurately determine the similarity of the design included in an image, such as a registered trademark, is required in order to accurately search for the registered designs similar to the design of the product under development.
As an apparatus which determines the similarity between images to search for a similar image, the following apparatus is disclosed in JP 2000-20721 A (Patent Document 1): a method which determines the similarity between two images, on the basis of an autocorrelation coefficient of the brightness value of each pixel in grayscale texture images of the two images, periodicity feature information related to the periodicity of the distribution of the brightness values of the pixels in each region of the image, and statistical feature information related to the statistical distribution of the brightness values of the pixels in each region of the image.
However, the technique disclosed in Patent Document 1 determines only the similarity between the images. Therefore, even when the technique is used to determine the similarity between the designs, the accuracy of determination is likely to be reduced in the following case: the image includes an image region different from an image region in which a target object (hereinafter, appropriately referred to as an “object”) which will be the basis for design similarity determination is present; and the result of the process of determining the similarity between the images is reflected in the result of the process of determining the similarity between the designs, without any change.